In the casting of molten steel to make ingots, it is desirable for economical reasons in some cases to make the mold into which the steel is cast in two pieces. One piece, called an "ingot mold", resembles a rectangular or circular tube which is tapered such that the opening at one end thereof is larger than the opening at the other. The other piece, normally a flat cast-iron plate, is called a "bottom plate". The ingot mold is set on the bottom plate with the axis of the ingot mold vergital and the smaller opening at the top. Molten steel is poured from a ladle into a series of molds, which are usually set on railroad flatbed cars so that they can be moved about easily. As the steel solidifies, it contracts slightly creating a small clearance between the ingot and the mold walls. Upon completion of the solidification, a crane grasps the mold by lugs cast into the outside wall of the mold, and lifts it off the bottom plate, leaving the ingot standing on the bottom plate.
A major weakness of the above-described casting system is that steel will leak between the mold and bottom plate unless a gasket or some other sealing material is installed between the surfaces of the ingot mold and bottom plate. The leaks of molten steel are dangerous to personnel in the area, damage railroad equipment on which the molds are set, and form a fin at right angles to the axis of the ingot. This fin is a waste of steel and must be removed by flame-cutting or sawing so that the ingot can pass easily through the rolling mill.
A number of procedures have been tried and proposed in the past for solving the above-mentioned problems in the casting of steel ingots. However, all such prior techniques and proposals have been proven to be unsatisfactory in at least one respect.
One prior procedure to prevent leakage of molten steel between the ingot mold and bottom plate has been to put steel strips into the gaps. However, these strips cannot fill any gaps smaller than their thickness, and a good deal of operator observation, time, and judgment is required to locate the existence of any gaps and fill them properly.
Another prior art procedure to is pack the spaces with refractory mortar. This is done conventionally from the outside of the mold, which results in mortar not getting through the gap to the inner part of the mold. Thus, the steel still leaks at least a part of the way from the inside of the mold to the outside (a distance that can be as much as 8") so that a fin is still formed. While the placing of mortar from the inside could solve this problem, such a procedure would result in refractory inclusions in the ingot, and is dangerous to personnel who would have to be lowered into a hot mold (sometimes 8' deep).
Another prior procedure is to put "clay rope" on the bottom plate before the mold is set, the clay rope configured in an outline to mesh with the shape of the mold where it contacts the bottom plate. "Clay rope" conventionally refers to a plastic tube (e.g., polyethylene) filled with a mixture of clay and water. The mold squashes the clay rope as it is set on the bottom plate, and the clay breaks out of the tube and effectively fills the gaps between the mold and plate. However, it is quite difficult to locate the molds on the bottom plates in the same place every time because cranes utilized to do so are not controllable in such a fine manner. Thus, personnel must guess where to put the clay rope so that the mold will match the rope configuration. Further, especially in the case of large bottom plates, it is difficult for personnel to lay the rope out properly because the plates are hot and have normally just been sprayed with a protective coating. Sometimes this problem is overcome by the crane operator suspending the mold just a few inches above the bottom plate while the clay rope is moved under it. However, this creates a serious risk of injury.
According to the present invention, all of the above-mentioned difficulties are overcome. According to the present invention, a method and product are provided that effect precise location, safety, and time savings in the placement of sealant between an ingot mold and bottom plate.
According to the present invention, a method of making a sealing structure adapted to be disposed between a metal-casting ingot mold and a bottom plate is provided. The ingot mold has a circumferentially extending bottom portion, and the method utilizes a cardboard sheet, an elongated flexible sealing element (preferably clay rope) and an adhesive system. The flexible sealing element can be laid out in a production operation in exactly the right configuration for any ingot mold. The sealing element is placed on the cardboard sheet so that it assumes substantially a closed configuration on the sheet corresponding to the circumferentially extending bottom portion of the mold. The sealing element is affixed to the cardboard sheet solely with the adhesive system. The adhesive system may comprise cold glue and tape, but preferably comprises hot glue. The hot glue is first placed on the cardboard sheet in the proper outline configuration, and the sealing element (e.g., clay rope) is then disposed on top of the hot glue immediately after its application.
In order to facilitate utilization of the cardboard-mounted sealant, preferably the cardboard sheet is selected so that it has at least one dimension thereof greater than the corresponding dimension of the mold with which it is designed to operate, providing an overlapping portion. The operator grabs the overlapping portion during use, and by moving the cardboard sheet by grasping the overlapping portion, the operator is able to exactly position the sealant in place as the ingot mold is being lowered, without a safety risk.
In order to facilitate transportation of the cardboard-mounted sealant from the manufacturing location to a steel mill, it is desirable to place the sealing element on the cardboard sheet so that it is offset at a central portion of the sheet. The sealing element still conforms to the general configuration of the ingot mold circumferentially extending bottom portion (which is significantly wider than the sealing element), but it allows the cardboard to be folded without the sealing element overlapping itself. Once folded, the sheet is easier to transport. When the sheet arrives at the steel mill, the operator unfolds the sheet, places it on the bottom plate in proper position with respect to the ingot mold, and then the ingot mold is lowered onto the bottom plate, squashing the clay rope.
It is the primary object of the present invention to provide a method and product for sealing between the metal-casting ingot mold and bottom plate that allows precise location of the seal, is safe to use or practice, and minimizes the time necessary to place the seal. This and other objects of the present invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.